Java

This guide will help build Java projects on Semaphore.

Overview

Java and related tools are pre-installed in Linux machines. You can switch the active compiler using sem-version.

How to change Java versions

Java is available on Linux Ubuntu machines. To change active Java versions use sem-version. For example to switch to v11:

sem-version java 11

See artifacts to learn how to save and persist the built JARs.

Using Docker containers

Semaphore does not distribute pre-build images for Java. You, can, however, build your own images and use them with Docker Environments.

See the semaphoreci/docker-images repository for examples of Dockerfiles.

How to cache dependencies in Java

The cache tool automatically detects the presence of Maven directories and cache dependencies.

The first job in the pipeline must cache the dependencies:

export MAVEN_OPTS=-Dmaven.repo.local=.m2
checkout
cache restore
mvn -q dependency:go-offline test-compile
cache store

The rest of the jobs can use the cache directly to retrieve dependencies and compiled code:

export MAVEN_OPTS=-Dmaven.repo.local=.m2
checkout
cache restore

How to set up test reports

This section explains how to set up test reports (and flaky tests) for Java and Maven.

1. Add the Surefire plugin to the pom.xml

   <build>
       <plugins>
           <plugin>
               <groupId>org.apache.maven.plugins</groupId>
               <artifactId>maven-surefire-plugin</artifactId>
               <version>3.0.0-M5</version>
               <configuration>
                   <reportFormat>xml</reportFormat>
                   <outputDirectory>/tmp</outputDirectory>
               </configuration>
           </plugin>
       </plugins>
   </build>

2. Run the tests

   mvn test

3. Create an after_pipeline job with the following command:

   test-results publish /tmp/junit.xml

Complete example

version: v1.0
name: Java & Maven Example
agent:
  machine:
    type: e1-standard-2
    os_image: ubuntu2404

blocks:
  - name: Setup
    task:
      env_vars:
        # Set maven to use a local directory. This is required for
        # the cache util. It must be set in all blocks.
        - name: MAVEN_OPTS
          value: "-Dmaven.repo.local=.m2"
      jobs:
        - name: Dependencies
          commands:
            - checkout
            - cache restore
            # Download all JARs possible and compile as much as possible
            # Use -q to reduce output spam
            - mvn -q dependency:go-offline test-compile
            - cache store
  - name: Tests
    task:
      env_vars:
        - name: MAVEN_OPTS
          value: "-Dmaven.repo.local=.m2"
      prologue:
        commands:
          - checkout
          - cache restore
      jobs:
        - name: Everything
          commands:
            - mvn test
            - mvn -q package
    epilogue:
      always:
        commands:
          - test-results publish /tmp/junit.xml